1. Field of the Invention
The present invention relates to a method of manufacturing a sandwich board. The invention further relates to a panel for application as a wall panel, a ceiling panel or a floor panel and to a sound insulating structure for use as a wall, a ceiling or a floor.
The invention particularly, although not exclusively, pertains to environments where space is scarce, such as in accommodations on board ships.
2. Description of the Prior Art
DE patent 34 44 992 C2 discloses a floor structure for accommodations on board ships and designed for sound insulation. According to this teaching a tile is manufactured by making out of 1 mm steel plate a shallow box with open top and pouring into this box a mixture comprising a PU based adhesive together with fillers. Once the compound has set, the tile is turned upside down and placed onto and adhered to a steel deck. Tiles made in this way are placed close together to build a floor cover layer. Where particular requirements to gas sealing prevail this floor-covering may be covered by a 0.5 mm steel plate adhered on top of the tiles and this structure may be topped by a carpet.
DE published application 27 06 969 B2 discloses a sound damping floor structure for use on ships and comprising a layer of mineral fiber material covered with a steel plating. The butt joints between sections of the steel plating are secured by fish plates arranged below the steel plating and on top of the mineral fiber material. The publication suggests adhering the fishplates to the steel platings by two-component polyurethane adhesive.
It is considered known in the art of ship building to build a sound attenuating floor structure by placing on top of a steel deck a mineral fiber wool layer, a first structural layer of steel plates, a layer of viscoelastic polyurethane, a second structural layer of steel plates and a carpet. Steel plates in the first structural layer are interconnected along the butt joints by spaced weldings for structural reasons. As part of the process of building this floor, the viscoelastic polyurethane is poured while in a viscous or fluent state on top of the first structural layer and screeded. Steel plates for the second structural layer are placed on top of the viscous layer and ballasted until the viscoelastic mass has set.
The inventor has discovered that the efficiency in terms of sound and vibration reduction capability of this floor is critically dependent on the accurate controlling of the thickness of the viscoelastic layer and on achieving full face contact between the viscoelastic layer and the steel plates of the two structural layers. However, lack of planety of the top surface of the viscous layer, unavoidable distortions of the steel plates, trapped air and the difficulty of inspecting the viscous layer while in the process of setting may give rise to difficulties during construction and imperfections in the result.
These difficulties are according to the state of the art encountered by using for the second structural layer steel plates of comparatively small formats, e.g. no more than 60.times.60 cm, by using heavy ballasting and by careful work. This complicates the procedure and the small formats of the steel plates of the second structural layer limits the structural rigidity provided by this floor. Furthermore, level offsets between adjacent plates require extensive filling, which has to be done using the same viscous compound as used below the second structural layer, which compound is costly and difficult to apply.